With Hurricane Dean still days away and on a path that as of Monday would spare Texas a direct hit, state officials were preparing for the worst Monday, warning residents that the Category 4 storm would still bring heavy rains and flooding to the southern coast.

"Keep an eye on the storm," Texas Gov. Rick Perry said during a press conference Monday, urging residents to gather and organize medications and important documents, fill their vehicle gas tanks and prepare a three-day supply of water and perishable food. "Be ready if the evacuation order comes."

• PHOTO ESSAY: Hurricane Dean

Officials have mobilized a massive response to the storm's landfall, and are particularly concerned about the south Texas areas of Galveston and Brownsville, where 44 lives were lost the last time a storm of Dean's magnitude hit the area in 1967, Steve McCraw, state director of homeland security, said.

The Brownsville region, also known as "the valley," is home to more than 200 nursing homes and 17 hospitals; 203,000 people live within the area in unincorporated "shantytowns" located within flood plains, and more than 133,000 residents of the area have been identified as "special needs" residents who are incapable of "self-evacuation," authorities said.

"It presents substantial challenges," McCraw said.

Though Dean is still on the Caribbean side of Mexico's Yucatan Peninsula and is expected to lose some steam as it crosses the peninsula, officials fear that the storm will reestablish itself after it is back over open water in the Gulf of Mexico.

The coastal regions of Texas are still recovering from a severe soaking caused by the remnants of Tropical Storm Erin, which along with other systems caused deadly flooding in Texas, Minnesota, Wisconsin and Oklahoma over the weekend, claiming 13 lives.

Gov. Perry has mobilized the National Guard and search and rescue teams, shipped 60,000 to 80,000 barrels of gasoline to gas stations in the Rio Grande Valley, and got a pre-emptive federal disaster declaration from President Bush.

The state sent six C-130 aircraft to Cameron County to help if any critically ill patients need to be evacuated from local hospital. Buses from the city, state, and military were on standby for possible evacuations, including a fleet of 700 sent by the governor's office. Another 600 buses were on standby in San Antonio.

"We learned a lot in 2005," Perry said, referring to the devastation wrought by Hurricanes Katrina and Rita. "We've applied those lessons, we've practiced...we are ready for this storm," he said.

On Sunday, officials in sodden south Texas left little to chance, readying planes, gasoline and hundreds of buses to get residents out in a hurry.

"We're preparing for Hurricane Dean just as if it is going to be a direct hit," said Johnny Cavazos, the chief emergency director for Cameron County at the state's southernmost tip.

A state of emergency was declared in the resort town of South Padre Island. About 3,300 jail and prison inmates in the area were to be bused to correctional facilities elsewhere by Sunday night.

In Washington, R. David Paulison, head of the Federal Emergency Management Agency, said up to 100,000 people might have to be evacuated from the state's southeastern coast and its immigrant shantytowns near the Mexican border. The storm is on course for northern Mexico, but could shift and hit the region around Brownsville, Texas, Paulison said.

Click here to track Hurricane Dean.

Flooding from what was left of Erin forced about 1,000 people to evacuate homes in Abilene on Sunday and was blamed for at least 13 deaths in Texas, Oklahoma and Minnesota.

The level of preparation for Dean was influenced by memories of two destructive hurricanes that hammered the Gulf Coast region in 2005.

"In part, it is because of the unfortunate events from Rita and Katrina," Cavazos said.

During Rita, the evacuation quickly turned into a nightmare of clogged highways, stalled traffic and sweltering heat, as motorists from the coast ran into residents fleeing Houston. Gas stations ran out of fuel and supplies, and drivers sat for hours on gridlocked evacuation routes.

Dean was a Category Four storm Monday, heading rapidly toward Mexico after crashing through Jamaica. The National Hurricane Center in Miami said it was projected to reach the most dangerous hurricane classification, Category 5, with wind of 160 mph before crashing into the Mexican coastline near Cancun on Monday night or Tuesday.

The storm was forecast to make landfall Wednesday, likely along the coast of northern Mexico, the hurricane center said.

Even if Mexico gets the brunt of the storm, Texas could still get soaked by Dean's outer bands of heavy rain, Cavazos said.

A Home Depot in Brownsville ran out of its supply of plywood Sunday as people rushed to board up windows, and about 60 people waited in line for a new shipment to arrive. Other customers crowded the store scooping up batteries, generators, water and flashlights, assistant store manager Edward Gonzalez said.

"We're hoping it misses us, but it is a huge, huge storm," said Gonzalez. "Everyone says they're not going to take chances. They're going to board up windows and be ready to ride it out."

"Being this prepared is expensive and, at times, it's inconvenient, but I'd rather be safe than sorry," Cavazos said.

The Associated Press contributed to this report.